A method for producing a semiconductor thin film for electronic devices of ZnS, GaAs, Si etc. or an insulating thin film of Ta.sub.2 O.sub.5, Al.sub.2 O.sub.3 etc. includes a vapor deposition method wherein starting materials of the thin film are vaporized and transferred onto a substrate. If a vapor pressure of the starting materials is low at room temperature, i.e. less than about 1 torr, the starting materials may be heated or chemically reacted with a reactive carrier gas to promote vaporization.
For example, if an electroluminescent (EL) film is prepared from ZnS and Mn by a heat chemical vapor deposition (CVD) method, a horizontal type vapor growth apparatus as shown in FIG. 3 is generally employed. In this apparatus, a reaction tube 1 includes two reaction tubes 2a and 2b and is surrounded with electric heaters 3a, 3b and 3c. A starting material ZnS 11 is placed in the reaction tube 2a and a metal (Mn) material 12 is placed in the reaction tube 2b. Substrates 10 are put on a holder and placed a little apart from the reaction tubes 2a and 2b. A baffle 4 for promoting the mixing of gas is arranged between the substrates 10 and the reaction tubes 2a and 2b. The electric heaters 3b and 3c heat to a desired temperature the reaction tubes 2a and 2b into which a carrier gas is introduced and starting material gas is transferred onto the substrate through the baffle 4 to form a ZnS:Mn film on the substrates 10.
In recent years, it has been desired that the CVD film having good qualities is grown in a large area of more than 100 cm.sup.2. An apparatus which can produce such high quality CVD film at low cost and in large quantities is also desired. However, in order to realize the above desire, there are three problems to be overcome.
(1) Since the substrates become larger and heavier, a running lift can not be used and an accumulation on a reaction tube wall is attached to the substrate.
(2) If the horizontal reaction tube is made a large scale, convection of gas in up and down directions occurs meaningfully, so as to cause nonuniformity of deposited film thickness in up and down directions between two substrates or in the same substrate.
(3) A conventional vertical apparatus for a large area substrate cannot ensure a position where solid starting materials are placed.